Physics 2002 JAMB Past Questions - Question 16: A ray of light wnich strikes a glass slab from air at normal incidence passes through the slab

Correct Answer

C

Explanation

When a ray of light strikes a glass slab from air at normal incidence, it means that the light ray is approaching the surface of the glass perpendicular to the surface. In this case, there is no deviation in the path of the light ray, and it continues to travel in a straight line through the glass slab.

At normal incidence, the angle of incidence (the angle between the incident ray and the normal to the surface) is 0 degrees. According to Snell's Law, which describes the behavior of light at the boundary between two different mediums, the formula for calculating the angle of refraction (the angle between the refracted ray and the normal to the surface) is:

\[n_1 \cdot \sin(\theta_1) = n_2 \cdot \sin(\theta_2)\]

Where:
- \(n_1\) is the refractive index of the first medium (in this case, air).
- \(n_2\) is the refractive index of the second medium (in this case, glass).
- \(\theta_1\) is the angle of incidence.
- \(\theta_2\) is the angle of refraction.

Since the angle of incidence is 0 degrees (normal incidence), \(\sin(\theta_1)\) is 0, and therefore, \(\theta_2\) is also 0 degrees. This means the light ray passes through the glass slab without any deviation or bending. It continues to travel in a straight line, though its speed and wavelength may change due to the change in the medium (from air to glass).

In summary, when a light ray strikes a glass slab from air at normal incidence, it passes through the glass slab without changing its direction, and there is no refraction.